In many industrial and consumer applications there is a need to analyze optical data and pictures. There is a trend towards highly integrated photosensitive pixel arrays (camera elements) integrated in a CMOS circuit or ASIC.
These devices may be used, for example, in security applications, IT products and optical communication networks. There is a huge variety in specifications such as number of pixels, spectral response and speed. Another important property of a photodetector or a photosensitive device is the quantum efficiency (QE) which indicates the device's electrical sensitivity to light. Depending on the specific application or device different definitions for the quantum efficiency are used. Typically, the quantum efficiency is a function of the wavelength of the incident light and may be used as a performance measure for the photosensitive device at different wavelengths.
When several photosensitive pixel elements are arranged in an array, cross talk between two or more photosensitive pixel elements may be an issue.
In the context of what is disclosed in this document, a photodetector is a device capable of converting electromagnetic irradiation into an electrical quantity, such as voltage, current, resistance, etc. Typically, a wavelength of the electromagnetic irradiation is within a range that is visible to the human eye or adjacent to the visible wavelength range, such as infrared light or ultraviolet light. Nevertheless, it is also possible that a specific photodetector is configured to detect electromagnetic radiation in another wavelength range.
A single photodetector may be used for providing a single electrical signal indicating e.g. a brightness of an incident radiation. Another possible application of a photodetector is within image sensors, where a plurality of photodetectors are arranged in an array. Typically, a photodetector is responsive to a fixed or predetermined range of the wavelengths.